Saturday, July 9, 2016

Viking Vibes and Mars Memories: Viking Forty Years Later, Part Two - Did Viking Discover Life On Mars?

Viking 1 surveys the "Big Joe" rock at Chryse Planitia. NASA image.

You should go there, it is so nice, Mars.
You should be
there, it's out of sight, Mars.
You should see it, it ain't so
high, Mars.
You should be there, up in the sky, Mars.

- Title track from Dexter Wansel’s Life On Mars LP, 1976

Throughout the 1970s, pop culture references to “life on Mars”
were inescapable. The late David Bowie sang about it on his album
Hunky Dory, and musician
Dexter Wansel even made a sci-fi funk album called Life On
Mars, released in 1976 (the year
of Viking). Science fiction, of course, had bandied about the
possibility of “little green men” on our neighboring planet for
decades.

But did Viking really discover life
on Mars, in any way, shape, or form? Did
the “little green men” exist on a microbial
level? This
debate continues to this day. Read
on, and make your decision:

Point:
Viking Didn’t Discover Life On Mars

There were three biology experiments aboard each of the Viking
landers: the pyrolytic release (PR) experiment (principal
investigator: Norman Horowitz, Caltech), the gas exchange (GEX)
experiment (PI: Vance Omaya, NASA’s Ames Research Center), and
Labeled Release (or LR, whose PI was Gilbert Levin of Biospherics
Inc.). A fourth experiment, the “Wolf Trap” developed by Dr. Wolf Vishniac of the University of Rochester, was axed due to budget cuts
in 1972.

Let’s focus mainly on the results from the LR experiment. The
January 1977 issue of National Geographic explained how LR
worked: “[A] radioactive nutrient is added to a soil sample in the
hope that something will digest it and give off radioactive carbon
dioxide. A count is made to determine any background radiation prior
to the test. Martian atmosphere and soil are added to the chamber,
and the latter is sprayed with tiny drops of nutrient. As with the
gases in the PR experiment, these carbon compounds contain
radioactive carbon 14. As the soil incubates, a detector looks for a
rise in radioactivity, indicating Martian organisms are metabolizing.
After a week or two the soil is squirted with a second course of
nutrient. The detector continues its watch.”

Viking's biology package. NASA graphic.

Within weeks of Viking 1’s July 20th landing, both the
GEX and LR experiments showed hopeful results that some kind of
abundant microbial life might exist upon the Red Planet. LR
especially suggested that a form of “exotic” life had taken root
on Mars, as the experiment initially yielded high counts of
radioactive carbon dioxide. But this excitement soon faded; Nat
Geo reported, “...[B]oth the LR and the GEX leveled off.” The
PR experiment, too, initially showed promising results, but later no
organic compounds were detected. (For a more detailed recollection of
LR findings, please check out this link.)

Tim Mutch, leader of the Viking Imaging Team, wrote in the 1978 NASA
publication The Martian Landscape:

Since all three of the experiments designed to test metabolic
activity of a microbiota yielded “positive” results, it is
tempting to conclude that life exists on Mars. ...We now recognize
that the biological results can be explained by inorganic surface
reactions in the absence of any living forms. Strengthening this
conclusion is the absence of organic compounds, documented by a gas
chromatograph mass spectrometer (GCMS) experiment.

Counterpoint: Viking May Have Discovered Life On Mars

But Mutch also added:

...Surely this does not prove the absence of life on Mars, only
its absence at two localities purposely chosen to be bland and
featureless. It remains possible – perhaps unlikely, although
statistics in this instance have little validity – that life exists
elsewhere on Mars in some special environmental niche – or that it
existed millions of years ago.

Remember that Mars’ exploration was still (and is still)
very much in its stages of infancy, and as Mutch pointed out, the
Viking landers only had surveyed two small areas (Chryse Planitia and
Utopia Planitia). More modern robotic explorers, both orbiting and
roving Mars, continue to search for signs of past and/or present
life, and evidence of water.

In addition, the results of the LR experiment are still subject to
debate. Gilbert Levin, LR’s principal investigator, insists the
Viking findings require further review to this day. He asserts that
microbes in the samples observed may have been killed by the
experiment itself. An email from Levin published in the July 2016
issue of Air & Space partially stated:

What actually happened on Mars was that the LR gave positive tests
for life. Loss of activity of the soil occurred while the soil sat
over two- and three-month periods at about 20 degrees Celsius (68
degrees Fahrenheit), strongly indicating that the organisms in the
soil, isolated from their environment, in the dark, and at a high
temperature for them, had died. A variety of other test and control
runs by the Viking LR all indicated life over chemistry. But because
another Viking instrument did not find organic matter in Martian
soil, scientists concluded life was not present.

Levin added passionately, “It is time to re-examine the Viking LR
data, which I contend did show extant microbial life in the topsoil
of Mars.” Who knows; perhaps there’s life – literally, and
figuratively – left yet in the Viking program.

Do you think the Vikings found life on Mars? Feel free to discuss
your thoughts in the comments.